To a British audience, it might seem an odd question to pose to a sitting governor of a US state – akin to asking whether the Earth was round, or if he believed apples fall to the ground because of gravity.

But what witchcraft is at work that requires a man bent on becoming leader of one of the most scientifically advanced nations in the world to deny a theory so universally accepted?

Put simply, politics.

A Pew poll in 2009 found a majority (54%) of Republican voters believed in evolution.Similar polling in 2013 found far fewer Republicans (43%) believed in evolution. In just four years, disbelieving Republican voters had switched from a minority to a majority.

Most Americans still believe in evolution. It’s likely most Republican politicians believe in evolution, albeit quietly. But increasingly the party’s base, those that turn out to vote in presidential and midterm elections, do not. To remain in power, some politicians must pander to this base, regardless of how discordant it makes them look to the rest of America or indeed the Western world.

The increasing polarisation of American politics is also at play. A general mistrust of science has come to represent the default position of many Republican voters, hence similar obfuscation on matters of climate change. The longer this persists, the more entrenched these views become.

Walker’s party has compromised on truth to retain power. It won’t last; relying on an ageing vote is unsustainable. Yet until the party itself evolves, Republican politicians will continue to be laughed at around the world.